Preservation of snow
Watering and water injection
Watering and water injection of the snow is sometimes used to harden the surface and create safe competition conditions in alpine, snowboard and ski jumping. Added water, followed by colder temperatures and grooming will increase the density of the snow. This is sometimes necessary for slalom, giant slalom, half pipe as well as in the landing zone of ski jumps. The actual watering process takes a long time and is complicated, and should be done only by experienced organizers or with expert advisors present. Before the watering starts, the weather forecast must be checked since changing temperatures will affect the process.
Depending on the size of the hill or course that is being watered, the process may take several days and demand lot of equipment and manpower. First the grooming machine creates a “potato field” to open up the snow surface such that water can easier sink in. All equipment (hoses, bamboo poles, rope, helmets, etc) should be brought to the top of the hill/course where the watering starts. The hoses are rolled down and connected to a hydrant such that the watering can take place on the hill/course both above and below the hydrant. The hoses are roped to bamboo poles that can be used as support if needed.
The crew is divided into groups that hold the hoses (in its entire length), and with two persons by the nozzle. Those two persons make sure the whole snow surface is being watered. Because the water pressure is high, it is important to coordinate with a person in the pumphouse via radio in case the pressure needs to be gradually turned up. The snow is watered until it changes colors, first to grey then to blue.
The process is repeated down the hill/course. After the hoses have been moved and connected to new hydrants, it is important to check that they have no sharp bends before water is turned on. This will secure that the high water pressure does not cause any dangerous situations with a “wild” hose.
Use of water injection equipment has become popular among World Cup and Olympic Games organizers. The injection is done by connecting high pressure water – via hydrants and hoses – to an aluminum bar with small nozzles who spray water 20 – 100 cm down into the snow. The process will create thousands of small holes where the snow around the holes are saturated with water. This snow will freeze due to heat evaporating from the holes or due to cold air sinking down into the holes.
This process also takes long time, and the safety due to the high water pressure in the water injection bar and hoses must be prioritized. When the aluminum bar with nozzles is moved it is important that the bar is not turned upside down and cause the nozzles to be filled with snow. The nozzles should not touch the snow until the water flows through them.
Each injection takes only 2 – 5 seconds, depending on the snow density and depth. First the water digs a hole, then fills it almost to the snow surface (sounding similar to when filling a bottle). The bar is then dragged (not lifted) downhill 5 – 10 cm and the process repeated. The bar must always be used perpendicular to the direction of the race course. The area next to the safety fences and the jump tables are not water injected.
The number and size of teams with equipment for watering and water injection depend on the length of the course and number of crew members available.
- 15-30 meter with snowmaking hoses
- Tools for opening and closing hydrants
- Nozzles or water injection bar (ett sett har som regel 3 rør)
- Bamboo poles to assist holding the hoses (during watering)
- Rope to assist holding the hoses (for watering)
- Drill with extra batteries and auger for drilling holes for the poles
- Propane or heatgun for melting nozzles or water injection bar if icing
- Whistle (for organizing and timing the activities)
- 1 person leading and organizing
- 1 person controlling the hydrant
- 5-8 persons holding the hoses or the water injection bar (depending on the length)
After the water injection it is important the the course is closed until the snow has been transformed (it is especially important that the holes from the injection are not covered).